全文获取类型
收费全文 | 1737篇 |
免费 | 116篇 |
国内免费 | 4篇 |
专业分类
化学 | 1287篇 |
晶体学 | 4篇 |
力学 | 65篇 |
数学 | 179篇 |
物理学 | 322篇 |
出版年
2023年 | 17篇 |
2022年 | 29篇 |
2021年 | 45篇 |
2020年 | 70篇 |
2019年 | 53篇 |
2018年 | 30篇 |
2017年 | 16篇 |
2016年 | 73篇 |
2015年 | 72篇 |
2014年 | 85篇 |
2013年 | 94篇 |
2012年 | 144篇 |
2011年 | 182篇 |
2010年 | 86篇 |
2009年 | 82篇 |
2008年 | 112篇 |
2007年 | 137篇 |
2006年 | 104篇 |
2005年 | 86篇 |
2004年 | 64篇 |
2003年 | 51篇 |
2002年 | 37篇 |
2001年 | 21篇 |
2000年 | 20篇 |
1999年 | 11篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 13篇 |
1995年 | 6篇 |
1994年 | 11篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1985年 | 5篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1977年 | 2篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1970年 | 2篇 |
1917年 | 2篇 |
1910年 | 2篇 |
1895年 | 2篇 |
排序方式: 共有1857条查询结果,搜索用时 62 毫秒
101.
N‐(2‐Ethylhexyl)carbazole: A New Fluorophore Highly Suitable as a Monomolecular Liquid Scintillator
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Eva Montbarbon Dr. Fabien Sguerra Dr. Guillaume H. V. Bertrand Élodie Magnier Dr. Romain Coulon Dr. Robert B. Pansu Dr. Matthieu Hamel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(34):12074-12080
The synthesis, photophysical properties, and applications in scintillation counting of N‐(2‐ethylhexyl)carbazole (EHCz) are reported. This molecule displays all of the required characteristics for an efficient liquid scintillator (emission wavelength, scintillation yield), and can be used without any extra fluorophores. Thus, its scintillation properties are discussed, as well as its fast neutron/gamma discrimination. For the latter application, the material is compared with the traditional liquid scintillator BC‐501 A, and other liquid fluorescent molecules classically used as scintillation solvents, such as xylene, pseudocumene (PC), linear alkylbenzenes (LAB), diisopropylnaphthalene (DIN), 1‐methylnaphthalene (1‐MeNapht), and 4‐isopropylbiphenyl (iPrBiph). For the first time, an excimeric form of a molecule has been advantageously used in scintillation counting. A moderate discrimination between fast neutrons and gamma rays was observed in bulk EHCz, with an apparent neutron/gamma discrimination potential half of that of BC‐501 A. 相似文献
102.
Angelo Paci Dominique Guillaume Henri‐Philippe Husson 《Journal of heterocyclic chemistry》2001,38(5):1131-1134
Three analogs of the cytostatic drug ifosfamide incorporating 1‐methyl‐2‐chloroethyl side chains were designed and prepared as an attempt to obtain drugs of lower toxicity. 相似文献
103.
The scanning transmission ion microscope (STIM) has been used to determine the intracellular mass of human cultured cells. A 4He+ microbeam of 2.0 MeV energy was chosen to obtain enhanced ion-energy-loss sensitivity through the micron-thick freeze-dried cells. Local sample mass calculation, based on energy-loss conversion by use of appropriate matrix stopping powers, was performed by use of dedicated software. The method was validated with epoxy resin sections and polymer foil as analogues of biological samples in the range of (intra)cellular thickness, 150 to 3000 nm. STIM analysis resulted in less than 5% error in mass determination. 4He+ energy-loss micro-spectrometry was performed on freeze-dried human ovarian cancer cells, the mean areal mass obtained was 120 microg cm(-2) (200 microg cm(-2) in the nucleus and 250 microg cm(-2) in nucleoli). This method is particularly useful for mass normalization of X-ray fluorescence yields resulting from particle-induced X-ray emission microanalysis (micro-PIXE). When performed successively these two ion-beam micro-analytical methods enable the mapping of true element concentrations within single cells. 相似文献
104.
Badro J Fiquet G Struzhkin VV Somayazulu M Mao HK Shen G Le Bihan T 《Physical review letters》2002,89(20):205504
We present a new method to separate the crystallographic and electronic phase transitions in hematite using x-ray emission spectroscopy and x-ray diffraction. Our observations, based on the behavior of a metastable high-pressure phase in the stability domain of the low-pressure phase, show that the electronic transition is preempted by the crystallographic transition. The former occurs only afterwards in the high-pressure phase, possibly as a result of a Mott transition. The idea that the electronic transition drives the transition in hematite is therefore invalidated. Such methods should help elucidate the mechanics and the driving forces behind a number of first-order high-pressure phase transitions. 相似文献
105.
106.
Guillaume Watier 《Semigroup Forum》1996,53(1):194-207
LetM be a monoid presented by <Σ;u=v> whereu andv are words on the finite alphabet Σ./ Deciding the world problem forM is still an open question, though it seems decidable and partial results exist. The remaining cases to solve are presentations
of the form <a, b; bva=aua>,u, v∈{a, b}⋆ The word problem is then closely related to the left-divisibility problem, as shown by S.I. Adjan who introduced a procedure
that “almost” allows to decide the problem. The main contribution, due to Adjan and Oganesjan, states that ifbva is an unbordered factor ofaua then the word problem is deciable. We restrict Adjan's procedure to study the case whenbva is unbordered, which allows us to extend Adjan and Oganesjan's theorem. More specifically, we show (Proposition 4.24) that
the word problem is decidable for presentations <a, b; bva=aua> with the only following condition: Inbva, the leftmost train ofb is strictly longer than the others. The following corollary naturally holds: The word problem is decidable for presentations
of the form <a, b; b
m
a
n
=aua>,u∈{a, b}⋆,m, n>0 相似文献
107.
We report here the first experimental observation of the flourescence of a LO phonon replica from the An=2 excitonic level in cadmium sulfide. A very simple theoretical interpretation is given. We present also experimental data about phonon replicas in the case of forbidden transitions. 相似文献
108.
The use of 2.8 MeV neutrons produced by the D(d, n)3He reaction should be taken into consideration in some applications of radioactivation analysis. The low number of elements
activable by these neutrons makes possible to minimize the matrix interference and the background below the characteristic
photopeaks. The very low dead-time of the spectrometric measurements permits the use of the maximum neutron flux available
now and in the future. The purpose of this paper is to define experimentally the sensitivity of determination for the 16 main
elements activable with a 400 keV Van de Graaff accelerator at a 2.8 MeV neutron flux of 2·106 n·cm−2·sec−1 on the sample. 相似文献
109.
Sans résumé 相似文献
110.
The development of the acidity and the relationship between acidity, catalytic activity, and the surface structure for niobium oxide supported on zirconia were investigated for a series of solids. The catalysts were active for 2-propanol dehydration only above a threshold in Nb loading. The acidity was studied by infrared spectroscopy of adsorbed 2,6-dimethylpyridine as a probe molecule, and the onset of activity was correlated with that of the formation of relatively strong Br?nsted acid sites. The variation in the abundance of these sites also correlated with the catalytic activity. Raman, IR, and UV spectroscopy results indicated that the active sites were related to polymeric Nb surface species. These results were compared to those previously reported for the WO(x)/ZrO(2) catalysts. 相似文献